Category: Electronics

Restoring-tektronix-2225-Oscilloscope – part two

Introduction

In part one we looked at the history of repairing a Tektronix 2225. At the end of part 1 the Tektronix 2225 scope is in a working order, but it has a lot of cosmetic issues and other issues. To summarize:

    •  The plastic back cover/panel is heavily broken
    •  The front panel is a France panel, and it is heavily broken
    •  Lot of knobs are broken / damaged. And some are missing.
    •  The case cover is in a bad shape
    • During the process of straighten the chassis one of the bolts pressed into the chassis broke of
    • Fuse holder is missing.

So to get the scope into a working and decent state requires some fair amount work, but obviously a lot of spare parts. The problem with spare parts for Tektronix scopes is: They are not cheap. So I started to look out on a complete none working Tektronix scope, which I could score cheaply.

And this took some seriously searching. Most of the scopes which are not functioning have also severe cosmetic problems as well. Most of the front panels have damage on them, back panels are missing, knobs are missing etc. And sometimes the phpto’s provided are not clearly showing the amount of damage. So it’s a gamble to buy one.

But one day I found a Tektronix scope which was more or less in a good shape. I could see the front panel had taken some hit, and could be damaged, but it could be alright either. It was hard to tell from the picture. It has some knobs missing, but with the knobs I already had I figured I could restore the scope. The listing mentioned:

This Tektronix 2225 Oscilloscope 50-MHz looks to be in good cosmetic conditions with signs of wear and previous use. (missing/damaged knobs)

Unit powers up; however, I lack the knowledge and equipment to test properly so it is being sold as-is.

Unpacked dims 19*16*7. See pictures for more details.

Please ask questions or indicate concerns prior to bidding. By placing a bid, you agree to all stated terms. All auctions are sold as advertised, as is and without warranty, unless otherwise stated in the item description. 
No software, power cords, or other accessories are included unless stated above. See additional terms of the auction below.

I figured I could take a gamble if I where to get 50% or so off.

Since this scope costs 200 dollar (which is about 172,40 euro's)
shipping is 88,50 dollar (which is about 76,28 euro's) 
total of 288,50 dollar (which is about 248,68 euro's).

And then I have to take into account the customs and import taxes / BTW costs.

So I did make a offer of 100 dollar (86,20 euro’s ), and to my surprise it was accepted. So I ended up paying:

scope costs 100 dollar (which is about 86,21 euro's)
shipping is 88,50 dollar (which is about 76,28 euro's)
total of 188,50 dollar (which is about 162,51 euro's)

Which saved me : 248,68 - 162,51 = 86,17 euro's.

The disadvantage of buying overseas are the customs costs. In this case I had to pay an extra 47,08 euro’s, which brings the total to 162,51 + 47,08 = 209,59 euro’s.
But.. If I had to collect, haunt down all the parts I needed, it will cost me properly a lot more.

So in the end I payed 110,00 euro’s for 3 scopes right ? So that is 1110 / 3 = 36 euro’s per scope. So to get this scope neat and decent again, it wil cost me : 209,59 + 36 = 245,59 euro’s. Considering that good working Tektronix scopes go for about 300,00 / 400 euro’s this is not a bad deal.

But sometimes this is not about the money you put in. It could be a labour of love, the passion about these equipment. And not to forget the knowledge gained when learning along the way.

The donor scope

Once the donor scope arrived and I tested it by powering on, and the scope works well. The scope is way out of specs.. but functioning. So I had one dilemma, should I used this scope, and calibrate it, or going ahead as planned, and restore the scope I wanted to restore in the first place ?

I decided to stick to the plan, and restore my own scope. And this turned out to be quite some work.

So what gear is needed to get this scope in a good shape ?

    •  Torx bit set
    •  Soldering iron
    •  Pliers
    •  Plastic bags
    •  Pieces of paper
    •  Camera (for taking photo’s, you can use the camera of your smartphone for instance)
    • And a lot of patience 🙂

Starting the restoration

The Tektronix 2225 has a lot of different screws, so every time when a part of a scope is taken apart, create a label, and describes where the screws / washers/ nuts / bolts / small part is coming from. But the label and parts in a plastic bag.
And before taking the scope apart make photographs, so it’s easier to put things together. Basically documenting every step in the tear down process.

Another tip is: start with taking apart one scope, and use the other scope as reference. In this case, since the various stages of repairing the scope which is going to be restored has lot of parts (screws etc) missing. Luckily I have another scope I could as reference, and I took a lot of pictures. And since I messed around with these scopes a lot, I can almost take them blindly apart, and put them back together again.

Another thing you have to take into account is safety. These scopes have high voltages inside of them. So be very aware of that. If you take precautions you should be safe. However: If you do not feel comfortable dealing with high voltages and CRT screens, then don’t mess with these devices.

I don’t feel comfortable messing around with high voltage stuff, so I always discharge CRT’s and capacitors. Since I don’t like to be zapped by them. And these capacitors can hold a lethal charge! Or they can hurt you really, really bad.

So: Always discharge the CRT and the capacitors in the power supply!

I noticed that letting a Tektronix 2225 overnight without the mains power cord plugged in, takes away most of the charge. Making discharge process a lot easier and safer. But whatever you do, don’t assume the capacitors are discharged in anyway! Safety first.

At this point It maybe sound like a very complicated thing to do, by taking two scopes apart, and “merge” the two scopes into one working scope again. But since all the troubleshooting is already done, and effort has been made to make sure that the donor scope is in a good working order.. It boils down to: unbolt things, and bolt them on again.

The important step is: document everything you do. This may sound like an extra step, which is going to take extra lot of time. But that isn’t the case. Figuring out how things must be put together while going through a pile of different screws and parts will take you much longer (if you ever can sort it out). So the whole idea is: prevent this from being a giant 3D puzzle. And you should be okay.

From experience I can tell that taking two Tektronix 2225 scopes apart, and building one scope again take a long day. So just take your time. Be patient keep your calm, and just go on. Since this is a hobby project, there is no deadline. During the restoration process my living room (which I try to keep clean from parts and broken equipment) turned into a workshop kind of place for almost a week. Scope parts where all over the place.

But this didn’t bother me, since I know it would be for a small period of time. And once I got my scope back into shape again, I could just bolt the donor scope somewhat together. I doesn’t have to work right ? I just bolt it together so I don’t loose part, and don’t damage the CRT (for instance).

Taking off the front panel

The first step is to dismantle the donor scope, by taking off the front panel. But first step is to discharge the CRT. Before the front panel is removed, the CRT must be removed from the chassis. When removing a CRT, do this very gentle. You don’t want to beak the CRT. Since a CRT is vacuum tube, it can implode, and then explode. So be very careful.

Before the CRT can be removed unsolder the wires which controls the rotation of the CRT. (The wires goes to a spool, forming a electromagnet.) Take not of the wires, as they are polarized.

When the wires are no longer connected to the main board, the CRT can be softly and gentled pushed forward, out of the chassis. The CRT is hold by pins at the back. So do this carefully. You probably want to wear safety goggles when doing this. If for some reason the CRT implodes, your eyes are protected. Better safe , then to be sorry) Store the CRT on a soft surface, or lay it flat. Make sure that you don’t damage the CRT (this can be expensive).

Once the CRT is out of the way, a couple of things needs to be disconnected from the front panel, by de-soldering: These are the Ground leads of the BNC, and the 47 Ohms resistors from the BNC’s. Also unsolder the wire which is for the compensation of the probes.

When all the wires are disconnected, the next step is to unscrew all the nuts of the front panel, and take off every knob. Be careful when removing the knobs. The can easily break off, since the ageing of plastic.
The next and last step before the front panel can be removed, is to remove every screw holding the front panel chassis part in place. So unscrew the screws from the main board, and from the chassis.

Once the front panel is removed, it can be put aside. The same procedure for removing the front panel must be done for the other scope as well. Only this time, make sure to remove the front panel very gently. So that the plastic switch gliders stay in place. Once the old front panel is removed it can be places back. This can be a fiddly job. Just take your time, and gentle place the front panel in place, without forcing it. Once the front is back into place, it looks like this:

Replace the bent part of the chassis

After the front panel is replaced I replaced the bent part of the chassis. Since I got the parts, this is a wise thing to do. The frame will be straight again. But in this case, one of the pressed in bolts are gone, so attaching the back panel isn’t going to work.

To remove this part of the chassis, the CRT socket must be removed from the back. This is easy to do, by removing the metal clip. Then rotate the socket, so that it can pushed inwards the scope. Unplug the Transformer connector. I decided to leave this one in place, and didn’t unbolt it from the chassis. Next unscrew every screw from the main-board, the chassis and part of the attenuation board.

Replacing this part of the chassis is relatively easy. Just place the chassis part in place, and bold on the main board, and to the reaming chassis. Reconnect the Transformer (make sure to plug in the connector at the right orientation). Re-seat the CRT connector. And place the metal clip back.

The last steps

At this point, all the knobs can be placed at the front panel. And make sure that every bold / nut is screwed on tightly, since they are attached to Ground. At this point the scope should look complete again. The steps to complete the rebuild:

    • Reconnect the probes compensation wire to the main board
    • Reconnect every ground wire onto the BNC’s again
    • Reconnect every 47 Ohms resistor
    • Reconnect the CRT anode

The end result

Once that is done, the scope can be tested, by putting a signal onto it. Once confirmed working, attach the cover, and this should be the end result.

At the end it’s nice to compare how the scope looked like, and looks after the complete restoration:

The original France front panel looked like this:

And now looks like this:

And the original back of the scope changed from:

Which now looks like:

The cover looked like this:

And now looks like:

All in all I’m very pleased with end results of this restoration / rebuild of the Tektronix 2225 scope. It’s amazing that at the end all the three scopes are working again. It took same fair amount of time and dedication. But again, I’m very pleased with the end results. And along the way, Dave and I had a great time working on these scopes. And I’m very thankful he helped me through the whole process.

And last but not least, all my Tektronix scopes are now in a working order, and this really puts a smile on my face. Because face it.. nerds going to be nerds. Below the two 2225 are working. The scope on the bottom is a Tektronix 2235

 

 

Restoring-tektronix-2225-Oscilloscope – part one

Introduction

The original Ebay purchases in 2017 for 3 Tektronix Scopes

This article was on my internal wiki, and finally came around to publish it. Once you started with electronics and learning, their may come a point in time you want to actually repair stuff. In my case this point in time came when I stumbled across a Ebay listing on 18 feb. 2017 which listed the following: “TEKTRONIX 2225 DIGITAL STORAGE OSCILLOSCOPE – LOT OF 3 FOR PARTS OR REPAIR” I started to mail the seller and asked a couple of question, like: do they power on, and “is the CRT working”.

I got a reply , but none of my questions where answered. The answer was:

“It is 3 ossilloscope sold in the state for parts Ideal for do-it-yourself-er. Attention heavy products.”

So the lot of 3 none working scopes where 150,00 euro’s. Since I didn’t know anything about their state (except “for parts”.) I decided to get the scopes for 75 euro’s where I wanted to pay a max of 120 euro’s. I finally negotiated a deal for 110,00 euro’s for 3 none working scopes. And so on 2 march 2017 I purchased the scope.

This for sure was a risk. I didn’t know anything about repairing scopes. Hell I even didn’t know if I would be able to repair the scopes in the first place. But I figured: In the worst case scenario I ended up with a lot of parts I could sell, and make even a profit on that.

The main concern was the CRT part, and therefore the high voltage section. But I got one trick upon my sleeve. And that trick came in the form of a good friend of my called Dave Donker. He is very knowledgeable when it comes down on stuff like this. And I talked him more or less into this project. And the deal was quite simple: If he would helped me to get the scope fixed, and we managed to get two scopes out of three working, he could take one working scope with him.

Of course this is still a gamble, since the scopes had still to be received by me.

Front side of two scopes arrived at my doorstep

The scopes arrived in two batches. I can’t recall the exact date’s they arrived, but the first batch was of two scopes, and one separate scope. And the first impressions where “What have I done .. “. The scopes where really , really dirty. They where in a a really bad shape. And one scope looks like it was dropped of a 10 floor building.

If you look at the photo at the right and click on it for a larger picture, you can see what I mean.

The scopes are dirty, but that’s not a real problem. There are knobs missing which is of a greater concern. But if you look really close on the top one, you see that the cover on the back has a large dent in it. More on that later on.

The reason for picking up the 2225 is not without a reason. The Tektronix’s 2225 scope has a really nice feature, and that is it can be set to 0.5 mV/Div. So it is really suited for measuring volt rails of power supply’s and look at the ripple’s. Another reason is: they are relative easy none complicated scope, since these scopes are pure analogue scopes. So no “digital storages” scopes.

The specs of the scope are:

    •  The Tektronix 2225 is a 50 MHz dual-channel analogue scope.
    •  It has a single timebase with a magnifier that allows displaying normal and magnified traces together on the screen
    •  Has no delay feature, only an X position control.
    •  The Y inputs feature a x10 magnifier that decreases bandwidth to 5 MHz but increases sensitivity to 0.5 mV/Div.

The Tektronix 2225 was introduces in 1987.

The excessive damage on the back of one of the scopes. (Click for larger picture)

The excessive damage on the back of one of the scopes.  When you look at the damage on the back of the one of the scope’s you can see how much force it took to make a dent like this. So my first idea was: this scope is only for parts, and it is probably beyond repair.

Restoration day

Detail look on the bent chassis.
As agreed One day Dave showed up, and we started to look at the scopes, and assess what we do with the three scopes. Most of the scopes made some rattling noises when you shake them about. So we had to open them up, to take a look inside. And by none of the scope we could see any crucial parts where broken of. Most rattling noises where from plastic mounting holes of the front plate, which where broken of. While the inside of the scopes where dirty, but looked intact.

We put aside the heavily damaged scope. And concentrated on the scope which looked somewhat alright. And one scope came alive without any problems. It just worked. So we put that one aside as well. The other one which looked alright had some problems. The trace wasn’t stable, and seems to disappear whenever it likes to do so, without any logical reason. So before trying to troubleshoot this problem we turned or attention to the heavily damaged scope.

A scope with serious damage

We noticed very soon that the damage to this scope must be quite severe, since the cover was really stuck, and we could not slice the chassis out of it. At closer inspection we noticed one of the points where the carry handle was attached to the cover has a dent as well. We tried with a hammer to get the cover off, we tried pulling it with both of us. One holding the cover, and one holding the chassis. But since the edges are sharp, and we didn’t want any injury we stopped that experiment.

Next we started with pliers, and screwdrivers to force the dent outside of the cover, and after several hours we managed to get the cover off, and we could take a closer look at the chassis. We expected that real heavy damaged near the power supply at the end of the main board, and that even the main power board would be cracked.

But to our surprise it look all in tact. We could see that on part of the chassis was bent inwards, so it would shorted out a part of the main board. So we didn’t dare to power it on and give it a try.

We turned our attention back to the other scope with has the disappearing traces. We figured we could perhaps replace parts. So we started to disassembling the scope. We soon discovered that it was a lot of work to take the scope apart. To remove the front panel we had to unsolder a lot of stuff , the BNC connectors are solder with a Ground wire and termination resistors to the main board.

Since it was already getting late, we decided that Dave took the two scopes with him, to create one working scope.

Two working scopes

Dave got the second scope working. (Click for larger picture)

On 16 March 2017 Dave posted the picture you see on the left, showing a working scope. He had to put much work into getting the scope working. He straightened the chassis of the heavily damaged scope, so that the cover more or less could be fitted on the chassis again, and he also made sure the chassis was not shorting anything out on the main board. At that point he could test the scope by powering it on.

 

And to our surprise the scope worked without any problems. So he decided to take out the main board of this damaged scope, and place it onto the the scope with the straight frame, to get that scope working again.

At that point we decided that the heavily damaged scope was just for parts (as we already concluded earlier.) After swapping the main board, Dave had a working scope again. And so from the three scopes, we had now 2 working scopes.

We started discussing what to do with the last none working scope. We concluded that the original idea was: That I wanted to troubleshoot and repair some broken equipment. And well.. we sure got one at hand.

So long story short: One day Dave showed up at my house, bringing one scope back, which was more or less put together, but in a state where it was ready to be powered on, so I could started troubleshooting the thing. Dave told me at that point, he did some investigation and he found a pre-amp which wasn’t working, but also told me, he hadn’t have any clue what was wrong that part of the circuit.

In part two, I’m going to focus on getting the chassis more straight, and start troubleshooting.

 

Fixing HP8012B Pulse generator

Introduction

I’ve bought a HP 8012B Pulse generator. The main purpose is to have a small device which I can use for generating clock signals. However the device I received needs some work. The buttons are sticky, and very intermittent. And I also notice that the transformer got really hot while operating the device. However the device produces some signals, since the buttons are intermittent, it’s kind of hard to get some useful signals.

Cleaning the buttons

If you’re like me and like to mess around with old HP gear, you properly know that HP gear is well build, and engineered in such way that taking a device apart is often easy, so that access to the internals of the device for maintenance or repair is easy.  Well with the HP8012B this is not the case. Maybe because this device is from the mod / late 70’s. The access to the internals of the device is quite easy. Both the left and right panels have a few screws. Once these screws are taking out the panels can be removed.

To get the front panel off, it’s quite a different story. It’s a fiddly job, and just take the time for it. Make sure to take pictures, before taking the device apart. There are some cables which must be de-soldered. Because the boards needs to be taken out. Well actually the boards can be leaved in, but then it’s quite tricky to get to the screws.

Once the front panel is removed I give all the potentiometers and switches a treatment with Deoxit. And after operating the switches and potentiometers for a while they feel much more reliable.

Replacing the capacitors

I suspect that the transformer is getting hot, due to some capacitors which gone bad. Before removing the electrolytic capacitors, make pictures. Because there are no markings for the plus or minus on the boards. I tested a few capacitors with my trusty HP 4261A LCR Meter, and found quite a few which are bad. So  I decided to replace every electrolytic capacitor. I also check a few resistors, but they where in spec, so no need to change them.

After replacing all the caps, I started to reassemble the device again. This is also not as easy as it sounds. A few wires from the transformer needs to be soldered onto the board, and since the transformer is heavy and bolted onto the back plate this means I have to keep the back plate somewhat in place, and solder on the wires, without burning anything with my hot solder iron.

 

After a lot of swaeting I managed to get everything back, and then I realized I forgot to replace the power on light bulb.. Doh..

Replacing the power on light

The power on light was burned out, so I needed to replaced this as well. Ideally you need to take the front panel off, or if the device is taken apart, replace the bulb at that time. Since I forgot to do that I have to take the whole thing apart again. Which I really don’t want to do. So I decided to try to place the new light bulb in place with the front cover attached. That’s not easy to do but I managed it.

The end result is one working HP8012B. This device is going to be used well in my lab. Very small device, ideal for generating clock signals. But it also allows me to test IC’s.

Replace the hard disk with a CF card in a HP 1660ES Logic Analyzer

Introduction

The bench top Logic Analyzers from HP namely the HP 1660E/ES/EP-Series have a builtin IDE hard drive. While this hard drive is not used during the boot process of the Logic Analyzer, the hard drive can be necessarily to  initialize some of the modules. Without the hard drive you may see errors like: not enough room to initialize modules. Since these drives are old, and can fail it might be smart to swap them out for a CF card.

 

The internal drive

The internal drive is known as HP part number 0950-2801 or F1385-69100. Which turns out to be a IBM 2.5″  2.1Gb laptop hard drive, model: DYKA-22160.

The plan is to replace this hard drive with a IDE CF Card adapter and a CF card of 2Gb.

Creating a Hard drive image

This should be the easy part. The process should go along the lines of:

    • Opening the Logic Analyzer
    • Take out the Hard drive
    • Hook the hard drive up to a computer with a usb external hard drive docking system
    • Create image from the hard drive
    • Restore the created image to a CF card

Well it turns out to be not that easy. At least if your using Mac OS that is. In the past I tried several USB devices which should be able to present a external hard drive as a usable device under Mac OS. However most of those external USB hard drive docking thingies are not working properly. Or the USB device itself is not recognized by my Imac, or the device is recognized, but doesn’t show any device in Mac OS.

“Why don’t you use windows for that task?” I can almost hear you ask. Well, I don’t have any hardware lying around to run a physical Windows system on. Well I have a very old laptop which runs Windows XP, but has only very slow USB ports, which brings a lot of it own limitations to the table.

I use a windows 10 virtual machine, but for that to work the USB device much be recognized by Mac OS for this to work.

So step 1 is to find some usb device which is able to read laptop IDE’s and CF card at least. This USB device must work under Mac OS.

Let me introduce Tccmebius TCC-S862

After a lot of searching I found the Tccmebius Harde Schijf Docking Station, TCC-S862-DE USB 2.0. Reading about this device it looks like it is supported by Mac OS. While not cheap, it’s not to expensive either. So for 28,00 euro found on Amazon it’s worth the gamble.

Quick review of the Tccmebius TCC-S862

There are a couple of different versions of the Tccmebius TCC-S862. The TCC-S862 can read  XD / TF-card/ MS (Duo / Pro) -card / CF-card / SD-card). It also is able to read IDE disk (3.5″ and 2.5″) and SATA I,II,III as well. Even claims to support SSD disk. And this is a lot of functionality in one USB device.

Other models have for instance USB 3.0 support. However I read that it gives problems. Some had to use a USB hub to get it working. Since I wanted a device which could read CF, SD, and IDE and SATA I picked up this model.

Using the Tccmebius TCC-S862

While this device works under Mac OS without problems, not all is good. The quality of the usb device feels very cheap plastic. Inserting a CF card is scary. It’s easy to bend the pins (already done that). The CF card goes in upside down. And it’s difficult to place.

Placing a 2.5″ disk is also tricky. The manual states to remove any metal backplate. And I know understand why. The disk sits flat against the backsite of the slot. this makes it impossible to see where the pins and the connector mate. Risking again bending the pins.

Making the drive image with the Tccmebius TCC-S862

Once the hard drive and CF card are inserted without causing any damage, the disks shows up as devices under Mac OS.

To get a list of hard drive devices use:

sudo diskutils list

That’s the good news. So the next step is to use the ‘dd’ command to create a image from the hard drive.

This is done by using for example the command:

sudo dd if=/dev/rdisk3 of=hp1660es_disk.img bs=4096

The bs parameter (Block Size) is determined by selecting a size which gives the best performance. However I discovered that by setting the bs to a high value, the error:

disk /dev/disk3 is unconfigured

popsup. I’ve tested this under Windows 10 in a VM, and also get errors with the device as I choose the number to high.

And yes, you can use the dd command under windows as well. I’ve installed git under windows, and that comes with some Unix tools, like the command ‘dd’.

So after leaving the bs parameter alone, I could create a disk image. Which is great. Placing the created hard drive image back unto the 2Gb CF card was easy to do with the dd command as well. I used a command like:

sudo dd if=hp1660es_disk.img of=/dev/rdisk3

( I removed the IDE HD at this point, and the CF card reported itself as disk3.)

So while the Tccmebius TCC-S862 is not very user friendly, it kinda works. Maybe there a better solutions out there, I don’t know. But having a device which actually works under Mac OS is a big plus. However think twice if you really want to buy this device.

Installing the CF card into the HP 1660 Logic Analyzer

After the CF card was prepared by placing the disk image on it, installing the CF card adapter and CF card into the Logic Analyzer was easy. For now I used kapton tape to make sure the CF adapter cannot short out, and also for now taped the adapter to the chassis. This doesn’t look nice, but as this is a temporarily fix, till I know for sure it works reliable. And we all know how permanent a temporarily fix is.. right ?

 

Finally I upgrade my soldering station

Introduction

This is my daily use soldering station. As can be seen I used this station quite intensive.  It’s a HQ/Solder 30. It can deliver 48Watts, and it is relativity cheap. When I bought it a couple of years ago, it was around 70 euro’s. The only problem I encountered was that the soldering iron itself stops working after a couple of years. With a replacement of 30 euro’s I could continue to use this station. And it worked very well I soldered a lot with this station. However I become more and more across PCB’s with big heavy ground planes, and this station simply can’t deliver the power (and thus heat). So after a lot of thinking, postponing the decision I finally got around to upgrade this station.

Requirements for the new solder station

As being said, I ran more and more across big ground planes. So the next solder station must be able to handle this. So I made a small list with requirements. These requirements are partially based on the experience I gained with the HQ/30 solder station. The short list of requirements:

    • More power then 48Watss
    • Active tips
    • Broad selection of tips (for example for “drag” soldering
    • Light soldering handle
    • Small footprint
    • Easy operation of the station itself.
    • It must be easy to swap tips (On the HQ I have to wait for it to cool down, which is a nightmare)

Why active soldering tips?

One of the requirements is to have active soldering tip. The reason is that the heating element is build into the tip itself, as the temperature sensor. This has the benefit of a good thermal couple, and thus a better transfer of heat. Also if the tip cools down due to a large ground plane (for example) it will recover faster.

However, there are some downsides to a active tips system:

    • The tips are more costly then the traditional tips
    • The solder station itself my be more expensive
    • The active tip is more likely prone to temperature drops

The last point can be addressed by making sure the solder station has enough power. Also there are now clones on the market which are cheaper then the established brands. Which also provides cheaper active tips. However, take into account that the materials used in the tips are less durable then the more expensive tips.

A big upgrade

I looked around for a good replacement, taking the requirements into account. And finally came to the conclusion it’s better invest more money, then trying to save some money and go for a cheaper solution, by looking into clones. So I bite the bullet, and decided to go for a JBC station. These stations are not cheap, but in every test I have seen, the JBC just leaves all the others behind in terms of performance. Furthermore I looked for example at Hakko stations, but the don’t have a small footprint. Well they have a large order of different tips, the JBC even has more choice. Also the operation experience is better on the JBC.

Comparing the two stations

This isn’t a review of both of the soldering stations, but the question might arise to compare the two stations. Well comparing the two stations isn’t really possible. I tried to solder some components on a big ground plane with the JBC, and it has no problems with it, while the HQ/30 isn’t able to melt the solder.  Also the time to heat up, the JBC reaches it’s working temperature in a few seconds. The HQ/30 takes it time. Comparing a 70 euro solder station to a soldering station which costs around 400 euro is not a fair comparison. And comparing a traditional solder tip to a active tip doesn’t make any sense either.

Being said that, the tips of the JBC comes at a price which is almost half of the price of the HQ/30 station. A standard jbc tip cost around 25 euro’s. Some tips are above the 30 euro’s.  And that’s something to consider. The HQ/30 at least for me, is a perfect soldering station, for general soldering jobs. The temperature may not be accurate, but for most of the things I solder, this is not a big deal.

Learning to solder with a cheap station as the HQ/30 is a good option, and personally a great learning experience. However now that the time has come to upgrade I decided to invest the money, and leave the cheap soldering stations behind. With this JBC I should have a solder station I can trust on, that it will perform and works when I need it. And the HQ/30 is going to be my second solder station.

What soldering station to buy when you start ?

When someone starts with electronics, the question which solder station to buy comes up. Often the suggestion is done to start with a cheap soldering iron / station. Obviously if you don’t know if your going to solder a lot, there is no point in looking at expensive soldering irons / stations. But if your starting out, and you got the money to spend, it might be smart to invest in a solder station like this one.  At the end, you get a soldering station which will last a long time, and the luxury of active solder tips. Which makes the heat transfer much more direct, and consistent. If you don’t have the budget, there are some clones, which seems to be very good also.

An easy extensible Raspberry PI Cluster

Introduction

For quite some time I want to play around with a PI Cluster. Of course “cluster” can mean many things. A Cluster can be combining all the CPU power of the nodes, to get more processing power. A cluster can also mean having couple of nodes to build a scalable platform like OpenStack. In this case, the purpose of the cluster isn’t that important. The thing I’m mainly interested in is build a frame which can hold a couple of PI’s. And the frame should be easy to extend, so that when there is a need for more PI nodes in the cluster, the frame is can be easily extended. At the end I came up with a working frame. However this implementation might not be suitable for everyone… More on that later on.

How this all started

With a friend of my we started to build a 20 node PI cluster. The cluster was split into two: 10 Nodes lived in my home, and the other 10 nodes lived by my friends house. We used a VPN to connect the cluster nodes together. This worked great. However when we used PI3 nodes, we needed cooling. And the current frame didn’t provide that. After a attempt to alter the frame to add cooling FAN’s I realized that it might be better to start from scratch. The reason for that was during the cluster was operational, we discovered the current frame could be improved by adding some features.

Designing the ultimate cluster

Well the “ultimate” is maybe a bit strong.. but since I wanted to redesign a cluster from scratch I decided that at least the following features must be implemented:

    • The nodes must be easy to remove or easy to be inserted into the cluster
    • The frame itself should be 19 inch so it could fit in a standard network rack
    • The nodes should be powered from a own power supply, and should NOT rely on PoE
    • The frame must be easy to extend
    • Each node should have proper cooling
    • It would be nice that each node has some LED’s to display status (preferred RGB LED’s)

Tackling the power requirements

Powering each node from a power supply is the hardest part to implement. After thinking about it I came to the conclusion that I could do this by developing a back-plane. This back-plane is then used to distribute the power from one Power Supply (PSU) to all the other nodes. This sound like a great idea. However it introduces a new problem:

How can I make a easy extensible frame when there is a back-plane. The answer to that problem was quite easily actually: by splitting the back-plane up into smaller back-planes. This is how I came up with a back-plane design which can hold two PI nodes, and can be extended by adding more back-planes together. And as it turns out: splitting the back-plane up into smaller back-planes also makes the manufacturing of the PCB easier.

By using a back-plane design it’s easy to come up with a PCB for each node , which would provide the interconnect between the PI node and the back-plane. Which makes it possible to remove or insert a PI node.

Tackling the cooling

Next thing problem to tackle was: How to keep the PI node cool, so that the CPU won’t overheat and throttle. I soon came with the idea to develop a PI Cluster HAT. This Cluster HAT solves a couple of other problems:

  • The HAT can be used to hold a FAN to cool the CPU (PWM controlled)
  • The HAT can be used to distribute the 5V to the back-plane
  • The HAT can also be used for other features:
    • Hold the connections for 3 RGB LED’s so they can be controlled by GPIO pins
    • Break-out I2C
    • Break out serial RX and TX
    • Break out 3V

Developing the cluster frame

Within three months I had the first version of a 10 node cluster working. It would take me another six months to get it to a a workable version. The final design uses 3 PCB’s:

  • A back-plane PCB with can power 2 PI Nodes and which are extensible.
  • A PI Cluster HAT with a lot of features (EEProm, PWN controlled FAN, 3 RGB LEDS, I2C, 3V, 5V power lines)
  • A Power board which connects the power of the PI node to the back-plane
  • A LED Board which holds the 3 RGB LED, which connects to the PI Cluster HAT

The frame of the cluster has mainly two parts: The frame which holds the PI tray. And the PI tray which holds the PI, the PI Hat with FAN, the Power Board and Led Board. The whole design is modular.

The downside of this is: To build this cluster frame, a lot of parts are needed, and the PCB’s must be soldered. So that’s why this might not be for everyone. However…

OpenSource is the way to go

Did I mention this whole design is OpenSource? No?? Well it is. And it’s on github for everyone to download. All the 3D models, Gerber files , schematics, a full hardware assembly guide is available. You can find it here

Fun with Ebay purchases

Introduction

A lot of the stuff in my lab comes from Ebay. Simply because this kind of equipment is hard or impossible to find in Europe. And if you find it, the seller is asking big money for it. Buying overseas is not cheap either, due to import taxes, and shipping costs.

And buying from Ebay has some risk to it. Of course, if you pay with Paypall, there is the “money back guarantee”. Most of the times this means shipping back the item

, and depending on the seller the shipments must be payed. If you buy stuff from Ebay you know all of this.

Most of the times however, it’s okay and there are no problems. And sometimes you find yourself in a situation which is just baffling.

What about a 54845A Infiniium Oscilloscope?

For some time I was looking for one of these. And I found a Ebay listing, made a best offer, which was accepted. For $1350,00 dollars the scope was mine. The scope was advertised as a working scope. So all in all it’s still on the high side. These scopes aren’t the best. But for what I have in mind it’s more then good enough.

And then the scope arrives

After a week and a couple of day waiting the scope was delivered. And well the package wasn’t that great. The scope could move around inside the box, which is bad. I wish that people sending equipment would learn to pack equipment so it can’t move around, with enough protection around all sides. In this case I feared the most. Luckily the scope itself was wrapped in a good amount of bubble wrap, and it didn’t destroyed the box it was in.

After unpacking and turning it on, the scope refused to boot. Due to a bad CMOS battery it want’s me to press F1 on the keyboard. And luckily a keyboard was included, so after hooking on the keyboard, and pressing F1, the scope booted into Windows, and started the scope application. The first impression was not that good. But if this was all.. I’m not complaining..

Self test time!

While the scope was booted I noticed some strange flickering and weird behavior while channel 1 was enabled. I disabled channel 1, and it looked good… for a while then some other glitches I could not explain. Hmm let’s do a self test.  And the self test failed on Video SRAM. And the second time  did a self test it failed on: “Tri State trig”. This points into the direction of a board called “A6”,which is a scope interface board.

It’s dirty… real dirty

So maybe the card has bad contacts, so I decided to remove the case, and take a look inside. And that is when I noticed a lot of dirt. I have seen dirt in machines, but this is really bad. I cleaned most of it. Cleaned the A6 board, and sprayed some Deoxit on the contacts. and reinstalled  the board. Unfortunately, the problem stayed.

Time to contact the seller

Now knowing that there is a problem with the scope I contacted the seller, which replied with: “I”ll see what I can do, and else send it back and you get a refund”.

After a good night of sleep I decided that sending the scope back in the original package, would be the end of the machine. The package would hold a second time. And I don’t have other packing materials. And it also means shipping costs, and the value of the dollar and euro.. so in the end it will cost me money, even if I get a refund. So I started to look online for a A6 board and could find one for 50 dollars. Which I bought. I let the seller know what I did to get the scope going. I also told about the state the scope is in, and that it’s not good. But that I went ahead and invested 50 dollar for a A6 card. The response I got was.. well i didn’t know if a should cry or laugh. the exact response was:

“All I can say is wow! That is amazing. Can’t thank you enough for doing that. I’m hoping it works out!”

Errr.. I don’t know how to respond to that.

Self calibration

I went ahead and tried to calibrate the scope by using the self calibration process. This is a straight forward process. It only takes some time to complete.

When I started the self calibration tool, it looks like the previous calibration seems to have failed on channel 2. Not a good sign. This is just the kind of problems I’m afraid of. These scopes have hybrid ADC’s. And it they fail, or there is some problem in the front-end.. it can be very hard to fix, and very costly.

And of course when I tried to calibrate the scope ,it failed. A lot of effort later by cleaning the hybrids the calibration process finally end successful. So now I only have to wait for the “A6” board, which is hopefully a working board, and I only have to swap the board, which is not very complicated.

In conclusion

When buying stuff on Ebay, there is always a risk that the item bought isn’t exactly what is advertised.And yes I could have shipped it back, and got a refund. However due to the state of the packaging I know for sure the scope wouldn’t make it in one piece. And spending 50 dollar seems the cheapest option. And the last thing I wanted was ending up in a discussion about a scope which was damaged during shipping.

To summarize: This scope was advertised as working, however:

      • Didn’t boot due to a dead CMOS battery (easy fix)
      • A6 board is defective (bad SRAM)
      • The machine wasn’t cleaned, and if I didn’t had to open it.. I would not know about the dirt inside.. which could easily destroyed the machine due to lack of cooling.
      • Calibration failed on channel 2. Luckily I could fix this. But this could have been a major problem.

This machine should have been listed as “untested for repair or parts”. If such a machine as this was advertised as such I wouldn’t even considering buying. It took a lot of time and to get it to a point of a good working scope. But I rather would have spend this time on the project I’m working on where I need the scope for in the first place.

Installing PyVisa on MacOS 10.14.6 (Mojave)

Installing PyVisa on MacOS 10.14.6 (Mojave)

In this article I had some trouble installing the NI-VISA library for py-visa. So this article is a quick update on that. This article describes what I did to test the NI-VISA library. And honestly I don’t know why it was not working.

First of all, when testing the installation of pyvisa with:

>>> import pyvisa
>>> rm = pyvisa.ResourceManager()
>>> rm.list_resources()

Make sure the equipment connected to the USB GPIB adapter is on. If the connected equipment is not on, you get a empty list of resources back.

Testing the NI-VISA library

The first thing I wanted to know was: When the NI-VISA library is not working, is that due to some configuration?

Testing can be a little annoying since when you reinstall the library, or de-install and (re)install you have to reboot your machine.  And I didn’t want to mess around to much, with the risk I wrecked some black magick library configuration. Which might be almost impossible to fix.

So I figured: Why not unpacking the installation package, and try the driver within the package directly ?

Unpacking a .pkg file under MacOS is really simply. First mount the Downloaded .dmg package. In my case: NI-VISA_20.0.0.dmg

Once it’s mounted, I changed to my home-dir, and created a test directory.

cd ~
mkdir test-nivisa
cd test-nivisa

Next I copied the installation package (NI-VISA_Full_20.0.0.pkg) to this test dir:

cp /Volumes/NI-VISA\ 20.0.0/NI-VISA_Full_20.0.0.pkg ./test-nivisa

Unpacking (or expanding) the install package is really easy:

pkgutil --expand nivisai.mpkg/.packages/NI-VISA_Full_20.0.0.pkg ./unpack

Note that the unpack dir is created during expanding the package. So don’t create the dir upfront! If you do the command fails with:

pkgutil --expand NI-VISA_Full_20.0.0.pkg ./unpack
Error encountered while creating ./unpack. Error 17: File exists

In the test dir where the package is unpacked, a lot of other packages can be found.  One of these packages contains the library which I’m after. However all the packages contains a file called “Payload” which is a gzipped tar file.

To unpack this file for each package, the find command is our friend:

cd unpack
find ./ -name 'Payload' -exec tar xzvf {} \;

This will unpack every Payload file in your current directory. Since the “v” flag is enabled (verbose) this outputs a lot of text (files which are untarred) There is a chance this will overwrite files, but this is not something I’m worried about, as long as I can use the NI-VISA library.

This library is called “VISA”, so a second find command is needed:

find ./ -name 'VISA'

Which gives the result:

.//VISA.framework/Versions/A/VISA
.//VISA.framework/VISA

Once I had the library I tested this with Pyvisa. This can easily be done in a virtual environment (not since I already tested this, the package pyvisa is already installed):

python3 -m venv env
pip install pyvisa
Requirement already satisfied: pyvisa in /Users/edwin/.pyenv/versions/3.7.3/lib/python3.7/

python3
Python 3.7.3 (default, Dec 4 2019, 15:11:28)
[Clang 10.0.1 (clang-1001.0.46.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyvisa
>>> rm = pyvisa.ResourceManager('./VISA.framework/VISA')
>>> rm.list_resources()
('GPIB0::9::INSTR',)
>>>

As can be seen on the last line:

('GPIB0::9::INSTR',)

The NI-VISA library works just fine. The actual library lives in:

/Library/Frameworks/VISA.framework/VISA

So I created a file .pyvisarc in my home dir (notice the dot (.) in front of the file!

This files contains:

cat ~/.pyvisarc
[Paths]
VISA library: /Library/Frameworks/VISA.framework/VISA

So know when I use pyvisa-info (pyvisa-shell) it works as well. pyvisa-info gives:

pyvisa-info
Machine Details:
Platform ID: Darwin-18.7.0-x86_64-i386-64bit
Processor: i386

Python:
Implementation: CPython
Executable: /Users/edwin/.pyenv/versions/3.7.3/bin/python3.7
Version: 3.7.3
Compiler: Clang 10.0.1 (clang-1001.0.46.4)
Bits: 64bit
Build: Dec 4 2019 15:11:28 (#default)
Unicode: UCS4

PyVISA Version: 1.11.3

Backends:
ivi:
Version: 1.11.3 (bundled with PyVISA)
#1: /Library/Frameworks/VISA.framework/VISA:
found by: auto
bitness: 64
Vendor: National Instruments
Impl. Version: National Instruments
Spec. Version: National Instruments
py:
Version: 0.5.1
ASRL INSTR: Available via PySerial (3.4)
USB INSTR: Available via PyUSB (1.1.1). Backend: libusb1
USB RAW: Available via PyUSB (1.1.1). Backend: libusb1
TCPIP INSTR: Available
TCPIP SOCKET: Available
GPIB INSTR:
Please install linux-gpib (Linux) or gpib-ctypes (Windows, Linux) to use this resource type. Note that installing gpib-ctypes will give you access to a broader range of funcionality.
No module named 'gpib'

So I really don’t know why it was not working the first time, and why it almost a day of pulling my hear out. There are two things I can think of:

I switch with my usb adater between a windows 10 VM maybe I didn’t release the adapter properly from Windows 10?

Or the adapter was not plugged in correctly ?

I tried switching from MacOS to my  Windows 10 VM multiple times, noticing it worked in Windows 10 perfectly, but not under MacOS.

Anyways, it works now. And hopefully the steps above might be useful to someone.

Comparison between Prologix and National Instruments USB GPIB controller

Introduction

Almost every electronics lab equipment has the possibility to be controlled remotely. This is almost always done by using IEEE-488. Also known as ” HP-IB” As HP called it when HP developed this 8 bit parallel bus.   It’s also know as “GPIB”. (General Purpose Interface Bus).

In the old days a dedicated computer card was used as a controller, to perform remote operations on the lab equipment.

Nowadays we have LXI for example, making it possible to remotely control devices over Ethernet network by using the TCP/IP protocol. This doesn’t mean GPIB isn’t used anymore. Even modern equipment can have a IEEE-488 interfaces. For example my Rigol DM3608 has a IEEE-488 interfaces and can be configured to understand a specific command set.

Use an IEEE488(GPIB) communication -adapter

Nowadays it’s more common to use USB GPIB controllers to remotely control the (old) lab equipment.  There are a couple of choices:

  • Use Prologix GPIB-USB
  • Use an IEEE488(GPIB) communication -adapter (Keithley or National Instruments for example)
  • These adapters may also be available as Ethernet controllers which plug into a LAN network.

However there are mainly two difference between the “brand names” and the Prologix:

For example the National Instruments (NI) USB controller present itself as a GPIB device. Whereas the Prologix presents itself as a serial device.

Which one to choose ?

If you look at the known brand names one, presenting them self as a gpib device, you notices these devices are not cheap. A new adapters can cost you as much as $1300,00 and no.. this is not a typo. While the Prologix adapter cost around $150,00 dollars.. So what’s the catch ? (there is always a catch).

And as always: It’s depends. Say for instance that you want to use an application from a vendor which only works with a GPIB device. The Prologix in this case won’t work. At least not out of the box.

On the other hand: If you’re about to write your own data log / measure applications, the Prologix might be a perfect solution, since  it’s a serial device, and you don’t have the overkill of using the NI-VISA drivers (for example)

Then there is of course the price. Luckily the GPIB USB adapters can be found relatively cheap second hand. I did found a genuine NI  GPIB USB-HS new in box for a around $150,00 dollar. Which brings these adapter in the price range of the Prologix one.

Comparing a Prologix and a NI GPIB USB-HS adapter

Since I have both types, let’s compare them in practice. To compare the adapters i’m going to use them in the following scenarios:

  • Using the adapters with a existing application from a vendor (Rohde Schwarz WINIQSIM) which is a Windows application
  • Use both adapters to write a own application, testing Windows 10 operating system and MacOS (10.14.6)

 

Prologix adapter

The Prologix USB adapter can be programmed by sending commands through a serial terminal. The GPIB address of the device can be set by sending:

++addr #

So for example to set the GPIB address to ‘8’:

++addr 8

There several commands, which allows to configure the adapter to one needs. Also it’s possible to update the firmware.  To talk to the adapter FTDI device drivers are needed, which are available for Windows, Linux and MacOS.

 

The national Instruments (NI) GPIB-USB HS adapter

The NI adapter needs NI-VISA drivers to be installed. These drivers are available for Windows, Linux and MacOS.As far that I know there is no firmware available for these adapters. There is a lot of information about how to install NI-VISA drivers etc. The only thing I needed to was to install the NI-VISA software, and plug in the adapter.

Using existing application WinIQSIM

The application WinIQSIM works perfectly with the NI USB-GPIB-HS. The application has the benefit of using a GPIB device, or serial. However I could not get a serial device to work with my Rohde Schwarz AMIQ. I either received a timeout, or a communication error. At the end I tried to use a null modem cable, but this gives me problems also.

The main problem when using the Prologx in the case is the speed setting. The applications “sweeps” the baud-rate setting. The Prologix however, doesn’t care about serial baud setting. So the WinIQSIM application gets confused, when trying to determine the baud settings. I tried several options, even disabling the “sweep”, however the application kept trying to find the highest speed it could communicate on.

It might be possible to implement a driver in NI-VISA, I didn’t test this however.

In this case: The NI USB adapter wins.

Writing my own application

In this test I’m going to test the python script which I wrote to remotely control my HP 8175A. In this case I’m going to use Python since this makes testing under MacOS and Windows 10 very easy.

I’m going to use two modules:

    • PyVisa
    • PySerial

On both systems I’m using virtual environments.

Test under MacOS

And this test ended very quickly.. I tried to use PyVisa under MacOS, and couldn’t get PyVisa to work. The library isn’t listing my GPIB device. I tried installing several versions of NI-VISA library. I even tried different version of NI-488.2 drivers.

>>> import pyvisa >>> rm = pyvisa.ResourceManager() >>> rm.list_resources() ('ASRL/dev/cu.Bluetooth-Incoming-Port::INSTR', 'ASRL/dev/cu.EEsiPhone-WirelessiAPv2::INSTR') >>>

Update: I finally got the NI-VISA driver working under MacOS. I just reinstalled the drivers, and when I give the path to the library (I tried that before, which didn’t work) it works:

>>> import pyvisa
>>> rm = pyvisa.ResourceManager('/Library/Frameworks/VISA.framework/VISA')
>>> rm.list_resources()
('GPIB0::8::INSTR', 'GPIB0::9::INSTR')
>>>

When I use the NI-VISA tools, the adapter is recognized without problems.

Test under Windows 10

So I moved to windows, installed NI-VISA library, and PyVisa and it worked instantly. No problems what so ever.

Next I tried pySerial on both platforms, and both worked just fine. Of course I needed to adapt the device name (under MacOS this is:

ser = serial.Serial('/dev/cu.usbserial-PX4UALP2')

Under Windows this is:

ser = serial.Serial('COM4')

The whole python script:

import serial

cmd = ['RST','DM0;DUR0,1s;IFM(CLOCK),,,1111','DM1;CFM(CLOCK);TSA0;CHD0,(CLOCK),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001;TSA9;CHD0,(END)','PM0;CD;(PROG1);CR7;CE;(END)','OM;POD 1','CM 0;CYM 1','UP;SA','LO']

ser = serial.Serial('/dev/cu.usbserial-PX4UALP2')

for c in cmd:
   send_cmd = c+'\n'
   ser.write(send_cmd.encode())

ser.close()

Conclusion

When using software which requires a GPIB device, then the easiest option is to chose for a USB controller which present itself as such a device. With some patience these devices can be bought relativity cheap. It might be possible to develop a own NI-VISA (or alike) driver for a Prologix USB adapter. Since I’m no expert in this, I didn’t do any research.

When using a NI USB GPIB controller (or alike) this will work under Windows. Under other Operating systems this might be problematic. With a lot of searching, and trying it might result in a working solution.  I couldn’t get the pyvisa to work under macOS the first time, after lot of trying and finally a reinstall, I could get it to work.

In my case the Prologix as the NI GPIB HS works on both platforms.

So the big question is: which wins ? Well if I only had Windows running as my Operating System, I definitely would go for the NI USB GPIB HS adapter, despite of the overkill of the whole NI-VISA environment.

And now that the NI adapter also works under macOS, I prefer the NI adapter over the Prologix adapter. Once the NI-VISA library works, it’s very easy to interact with the device. If however the NI-VISA lib doesn’t work.. or you simply don’t want the overhead the Prologix adapter might be the way to go, while keeping in mind when using vendor supplied software which relies on GPIB controller, the Prologix might not work..

Another thing to consider when using an adapter which relies on drivers like NI-VISA is when transferring software to other systems. For example when you write this awesome script in python for a specific device. When uploading this script to GitHub for others to use it, they need to install the (external) library. Which may be undesirable. In my case this is not really a concern.

However since I got both adapters.. I have the best of both worlds 🙂

Using a VFD IV-3A tube to build a simple counter – Part four

Introduction

In part three the rest of the counter is build, and the circuit is almost complete. The part which is missing, is the thing that makes it count. We  could simply add a 4 bits binary counter, but why not simulate a counter ?

The HP8175A

To simulate a simple 4 bits counter, I’m going to use my HP8175A. It’s big, it’s heavy, makes a lot of noise and eats a gazillion electrons per microseconds, and spits them out as heat. So what is not to love about this machine?

The interface of the HP8175A may take some time to get used at, but I loved it from the start. However to make it more interesting the HP8175A is programmed completely by IEEE-488. or GP-IB or a HP-IB  If you own a HP8175A and don’t have the possibility to remote control the machine, then study the user manual. It’s really not that difficult to program the HP8175A through the keyboard and knobs.

I used a National Instrument USB GPIB HS adapter to remote control the HP.

Remote control the HP8175A

To program the HP8175A a couple of steps must be taken. The HP8175A has so called “Module pages”. We need to:

    1. Setup on the Data Module the format: by setting up the POD and the duration.
    2. Setup on the Data Page the labels and bits which makes up the program
    3. Setup on the Program Page the program, the start end end labels, as well the times to run the program
    4. Setup the Clock page,
    5. And finally update all the settings and start the program

The IEEE-488 commands for the HP8175A is a bit cryptic, but this is the whole program:

RST
DM0;DUR0,1s;IFM(CLOCK),,,1111
DM1;CFM(CLOCK);TSA0;CHD0,(CLOCK),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001;TSA9;CHD0,(END)
PM0;CD;(PROG1);CR7;CE;(END)
OM;POD 1
CM 0;CYM 1
UP;SA
LO

Explanation of the program

The commands and parameters are separated by a ‘;’. So for example the second line contains 3 commands: DM0 and DUR0 and IFM (Data Module, Duration Fixed, and Insert ForMat label)

    1. Reset HP8175A to defaults
    2. Go to page: Data Module FORMAT and set DUration to fixed 1 second and Insert ForMat label CLOCK and enable the first 4 POD lines (bits) of POD0
    3. Go to DATA page module and ChangeForMat label to CLOCK and Set
    4. ToStartAdress; CHangeData 0, CLOCK end set bits up to address 9 and change label to END ()
    5. Go to Program Module page and set the label PROG1, Move Cursor Right 7  positions, clear the field and change field so it contains the END label
    6.  Go to Output Module page and set all PODS enable
    7.  Goto Clock Module page and Set Clock to Auto Cycle
    8.  Update and start
    9.  Return to local (stop remote control, and enable front panel)

Line 3 might require some explanation:

DM1;CFM(CLOCK);TSA0;CHD0,(CLOCK),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001;TSA9;CHD0,(END)

The part:

 TSA0;CHD0,(CLOCK),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001

is quite clever. The engineers at the time by HP really know how to implement this kind of stuff. The command TSA needs a start address, which is the 0. Next command changes the format label to “CLOCK”. And then comes the clever part.

Since we enabled only for outputs on POD 0, we can have 4 bits on each address line. So by placing the 4 bits separated by comma’s, each bit pattern is placed on a address line. And therefore, this command places each 4 bits starting from address 0000 to 1001 (0 – 9).

So it works like:

                 4bits  4bits                                4bits
Set start addr   addr 0 addr 1                               addr 9
/|\               /|\   /|\                                   /|\
 |                 |     |                                     | 
TSA0;CHD0,(CLOCK),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001

DECIMAL              0,   1,   2,   3,   4,   5,   6,   7,   8,   9

Let’s see the HP8175A in action

After sending the commands, the HP8175A is acting like a 4 bit binary counter:

Once I know the program is working I wrote a little pyton script using pyvisa:

import pyvisa
import time

# Small programm to remote control a HP8175A
# Using PyVisa with a NI USB GPIB-HS+

# Setup the resource manager
rm = pyvisa.ResourceManager()

#print(rm.list_resources())
# Open HP8175A
hp8175a = rm.open_resource('GPIB0::8::INSTR')

# Identify yourself!
print(hp8175a.query('IDN?'))
print(hp8175a.write('RST'))
time.sleep(5)

print(hp8175a.write('RST'))
print(hp8175a.write('DM0;DUR0,1s;IFM(CLOCK),,,1111'))
print(hp8175a.write('DM1;CFM(CLOCK);TSA0;CHD0,(CLOCK),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001;TSA9;CHD0,(END)'))
print(hp8175a.write('PM0;CD;(PROG1);CR7;CE;(END)'))
print(hp8175a.write('OM;POD 1'))
print(hp8175a.write('CM 0;CYM 1'))
print(hp8175a.write('UP;SA'))
print(hp8175a.write('LO'))